1. Field of the Invention:
The present invention relates to a fan control apparatus and a fan control method, for example, for cooling a heat generating portion in equipment by using a cooling fan.
2. Description of the Related Art:
In a conventional fan control apparatus which cools, for example, a power supply unit or an actuator of heat generating portions by using a cooling fan, the cooling fan is always made rotated when the power supply of the equipment body is turned on.
[Patent Document 1]
Japanese Laid-open Patent publication No.2001-56724
However, in the above mentioned conventional fan control apparatus, the cooling fan is always rotated whenever the power supply of the equipment body is turned on, so that there was a disadvantage that a rotation noise is always generated caused by the rotation of the cooling fan and the quality of the equipment goes down by the undesired sound in an environment where quietness is required.
Additionally, there is a method where the drive voltage is lowered such that the rotational frequency is dropped down and the like in order to reduce the rotation noise of the cooling fan, but there is a limit in order to achieve the operation with a satisfactory cooling function.
According to the control of the present invention, the subject matter lies in that the fan control is performed by a feedback using a temperature sensor and at the same time the cooling fan is stopped at the time of polling for controlling the time axis such that the rotation noise can be reduced.
The difference between the present invention and the patent document 1 will be shown hereinafter. According to the claim of this patent document 1, the fan control method has a feature that a register value corresponding to a measured temperature is transferred to a fan rotational frequency control IC so as to produce a drive voltage within the IC for controlling the fan.
The patent document 1 has a feature of controlling by means of SM bus since it is a general matter that the temperature in the equipment is measured by a temperature sensor for controlling the fan while in this point of view, firstly the temperature measured by the temperature sensor is converted to a voltage in the fan control method according to the present invention. Secondly, a sub microcomputer (micom) AD converts that voltage and downloads it to the micom as time-series data. Thirdly, the temperature data and set data are compared by a control program so as to perform the fan control. Fourthly, the fan operation voltage is an output of a 4-terminal regulator in a power supply circuit and controlled by H/L of FAN_CONT signal from the sub micom. Fifthly, there is a difference in that the present application does not use the special SM bus but uses an AD converting function of the sub micom for converting the measured temperature to data and performing a program control.
Especially, speaking of the difference of the present invention with respect to the patent document 1, there is a big difference in that a time axis fan control is added to the fan control by the temperature sensor when performing a local control by the sub micom without using the SM bus. When performing a fan control where the temperature control is preferential, the fan cannot be stopped, for example, for a few minutes at the starting time and moreover, it is impossible to set a constant stop period. A timer is used for setting a duration corresponding to the absolute time in order to stop the fan, for example, for a few minutes from the starting time of the equipment. After a few minutes elapse, it is shifted to a fan control by means of the temperature sensor.
The polling operation which requires an operation program to be renewed and the like for the equipment with respect to a server connected via the network continues less than approximately a few minutes after the equipment is activated, so that the purpose of the present invention is to stop the fan during that period in order to reduce noises and similarly to reduce power consumption.
In the patent document 1, in case of a fan control only by the temperature sensor, the fan is made stopped at the starting time and is turned on when the temperature becomes higher than the upper limit. When the temperature becomes higher than the upper limit, the fan rotates. Conversely, when it is lower than the upper limit, the fan remains in a stop state such that the temperature of the equipment increases rapidly. Consequently, the fan rotates again and cools the inside of the equipment. If the upper limit value is lowered, the fan repeats on and off in a short period such that a so-called hunting phenomenon occurs and it is impossible to make the stop period constant unless a time axis control according to the present invention is adopted.